Editing the Marker template

I've been struggling with some functionallity i would like to implement on my SMFPlayer.
The feature is to be able to move the timeline markers over the timeline while clicking/holding it and sliding it along the timeline (by so, updating the timestamp of the marker).
I thought about editing the template for the markers, but Blend is copiously insulting me when i'm trying to edit the Marker element...
Any idea ?